The present invention generally relates to the field of antennas, and more particularly, to an antenna which includes two vertically oriented orthogonal RF loop elements coupled to a ground plane and has a common center feed.
Conventional HF communications use ground wave propagation up to about fifty miles. For long distance HF communication, sky wave propagation is used. HF antennas have been used for both modes of propagation. For communications between 50 and 300 miles, near vertical incidence skywave (NVIS) propagation is used. Antennas typically used for NVIS applications tend to be very large and bulky. For example, some of these antennas are in the shape of inverted conical spirals and require up to 6 masts to support them. The diameter of an entire antenna of this type may exceed 200 feet and have a height of 100 feet. Most of these antennas require resistive loads which are very bulky and expensive because they must be able to dissipate high power. Such resistive loads are also required for antennas of this type to have wide bandwidth performance.
Therefore, a present need exists for an NVIS antenna that requires minimal resistive loading, has relatively compact dimensions, can handle high power loads, and has a large frequency bandwidth ratio.